Most of Santa Fe's Super Fleet consists of fairly new "widecab"
locomotives. The FP45's are the exception to this rule. These units
were the first to wear the modern Super Fleet scheme, as it was
applied to them as a test before the decision was made to paint new
locomotives in this scheme.
All of these locomotives were over 20 years old when they received
their current red and silver coats, and were then renumbered to the
100 series (same series as they were numbered when new). The FP45's
were soon renumbered to the 5990 series to make room for the new
GP60M's, and soon after were renumbered into the current 90 series.